Buffing is known as a processing method for smoothing a polishing target having a curved surface, for example, a resin-coated surface of an automobile and the like (for example, PTL 1). The buffing is a method of polishing the polishing target in such a manner that a variety of polishing agents are applied onto a circumference (surface) of a polishing wheel (buff) made of cloth or other materials and are then rotated.